a.

1. 不穩固的；不固定的；不牢靠的
   The table is unstable because one leg is shorter than the others.

   這桌子一條腿比其它的腿短，所以不平穩。

2. 易變的；動蕩的
   The price of gasoline is unstable.

   汽油價不穩定。

3. （性情）反覆無常的；不規則的
   He was emotionally unstable.

   他情緒易波動。

4. 【化】分解的；不穩定的

adj.

1. likely to collapse or change; not stable.
2. prone to psychiatric problems or sudden changes of mood.